Uplink Calibration for MIMO Hardware Chain Gain Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In MIMO wireless communication systems, accurate downlink channel state information (CSI) cannot be obtained due to differences in transmit and receive hardware chain gains, violating channel reciprocity, which affects the estimation of DL-CSI from uplink pilots in TDD systems and channel covariance estimates in FDD systems.
Innovation Solution
A method involving a terminal that estimates the downlink channel of each base station antenna and sends normalized values in the uplink to calibrate hardware chain gains, using a DL and UL signaling procedure to improve calibration accuracy and enable efficient control of MIMO gains.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hardware chain gains in BS are not calibrated, then the system operation is simple, but the downlink channel state information estimation accuracy deteriorates
Solution Approach 1:
The terminal performs self-calibration by autonomously estimating downlink channel responses from pilot signals and computing calibration values without external assistance. The terminal sends these calibration values to the base station, enabling the base station to self-correct its hardware chain gain differences, thus achieving calibration through the terminal's self-service capability.
Solution Approach 2:
The terminal pre-calculates calibration values based on downlink channel estimates before uplink transmission. By performing the channel estimation and calibration value computation in advance during the downlink phase, the system prepares correction data that will be applied during uplink operation, improving efficiency and accuracy.
2Measurement precision
If traditional calibration methods are used, then the implementation is simpler, but the calibration accuracy deteriorates and MIMO gains cannot be efficiently controlled
Solution Approach 1:
The patent replaces traditional physical calibration equipment (such as calibration antennas or measurement devices) with signal processing-based calibration. By using downlink pilot signals and channel estimation algorithms, the system achieves calibration through computational methods rather than physical measurement tools, improving accuracy while maintaining implementation feasibility.
Solution Approach 2:
The terminal uses its existing downlink channel estimation functionality (designed for other purposes) to generate calibration values. The same pilot signal reception and channel estimation mechanisms intended for channel state information acquisition are repurposed to provide calibration data, making the calibration process universal and integrated into existing terminal operations without requiring separate dedicated calibration hardware.
3Productivity
If no calibration is performed, then the signaling overhead is reduced, but the channel reciprocity is violated and TDD MIMO gains cannot be exploited
Solution Approach 1:
The calibration values are extracted from the downlink channel response information that the terminal already processes. By separating the calibration value computation from the main data transmission function and extracting only the necessary calibration parameters, the system minimizes the additional signaling overhead while preserving the essential calibration information needed to exploit TDD MIMO gains.
Data Source
Figure 1~2
Figure 3~4
AI summary
The present invention refers to a method for obtaining uplink calibration values in a terminal of a wireless communication system in order to enable a Base Station, BS, having a number of antennas to determine a respective hardware chain value for each antenna of the number of antennas, said method comprising the steps of calculating 1, by the terminal, an uplink calibration value for each antenna on the basis of a downlink channel estimate value for each antenna and a normalization value obtained from said downlink channel estimate values, and sending transmitting 2, by the terminal, the calculated uplink calibration value for each antenna to the BS. The invention further refers to a corresponding terminal 10 for a wireless communication system, adapted to obtain uplink calibration values. The present invention further refers to a corresponding calibration method for determining hardware chain values in a base station 20, as well as the corresponding base station 20 itself.